/*--------------------------------------------------
   CLOVER.C -- Clover Drawing Program Using Regions
               (c) Charles Petzold, 1998
  --------------------------------------------------*/

#include <windows.h>
#include <math.h>

#define TWO_PI (2.0 * 3.14159)

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
	PSTR szCmdLine, int iCmdShow)
{
	static TCHAR szAppName[] = TEXT ("Clover") ;
	HWND         hwnd ;
	MSG          msg ;
	WNDCLASS     wndclass ;

	wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
	wndclass.lpfnWndProc   = WndProc ;
	wndclass.cbClsExtra    = 0 ;
	wndclass.cbWndExtra    = 0 ;
	wndclass.hInstance     = hInstance ;
	wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;
	wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
	wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
	wndclass.lpszMenuName  = NULL ;
	wndclass.lpszClassName = szAppName ;

	if (!RegisterClass (&wndclass))
	{
		MessageBox (NULL, TEXT ("This program requires Windows NT!"),
			szAppName, MB_ICONERROR) ;
		return 0 ;
	}

	hwnd = CreateWindow (szAppName, TEXT ("Draw a Clover"),
		WS_OVERLAPPEDWINDOW,
		CW_USEDEFAULT, CW_USEDEFAULT,
		CW_USEDEFAULT, CW_USEDEFAULT,
		NULL, NULL, hInstance, NULL) ;

	ShowWindow (hwnd, iCmdShow) ;
	UpdateWindow (hwnd) ;

	while (GetMessage (&msg, NULL, 0, 0))
	{
		TranslateMessage (&msg) ;
		DispatchMessage (&msg) ;
	}
	return msg.wParam ;
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT iMsg, WPARAM wParam, LPARAM lParam)
{
	static HRGN hRgnClip ;
	static int  cxClient, cyClient ;
	double      fAngle, fRadius ;
	HCURSOR     hCursor ;
	HDC         hdc ;
	HRGN        hRgnTemp[6] ;
	int         i ;
	PAINTSTRUCT ps ;

	switch (iMsg)
	{
	case WM_SIZE:
		cxClient = LOWORD (lParam) ;
		cyClient = HIWORD (lParam) ;

		hCursor = SetCursor (LoadCursor (NULL, IDC_WAIT)) ;
		ShowCursor (TRUE) ;

		if (hRgnClip)
			DeleteObject (hRgnClip) ;

		hRgnTemp[0] = CreateEllipticRgn (0, cyClient / 3,
			cxClient / 2, 2 * cyClient / 3) ;
		hRgnTemp[1] = CreateEllipticRgn (cxClient / 2, cyClient / 3,
			cxClient, 2 * cyClient / 3) ;
		hRgnTemp[2] = CreateEllipticRgn (cxClient / 3, 0,
			2 * cxClient / 3, cyClient / 2) ;
		hRgnTemp[3] = CreateEllipticRgn (cxClient / 3, cyClient / 2,
			2 * cxClient / 3, cyClient) ;
		hRgnTemp[4] = CreateRectRgn (0, 0, 1, 1) ;
		hRgnTemp[5] = CreateRectRgn (0, 0, 1, 1) ;
		hRgnClip    = CreateRectRgn (0, 0, 1, 1) ;

		CombineRgn (hRgnTemp[4], hRgnTemp[0], hRgnTemp[1], RGN_OR) ;
		CombineRgn (hRgnTemp[5], hRgnTemp[2], hRgnTemp[3], RGN_OR) ;
		CombineRgn (hRgnClip,    hRgnTemp[4], hRgnTemp[5], RGN_XOR) ;

		for (i = 0 ; i < 6 ; i++)
			DeleteObject (hRgnTemp[i]) ;

		SetCursor (hCursor) ;
		ShowCursor (FALSE) ;
		return 0 ;

	case WM_PAINT:
		hdc = BeginPaint (hwnd, &ps) ;

		SetViewportOrgEx (hdc, cxClient / 2, cyClient / 2, NULL) ;
		SelectClipRgn (hdc, hRgnClip) ;

		fRadius = _hypot (cxClient / 2.0, cyClient / 2.0) ;

		for (fAngle = 0.0 ; fAngle < TWO_PI ; fAngle += TWO_PI / 360)
		{
			MoveToEx (hdc, 0, 0, NULL) ;
			LineTo (hdc, (int) ( fRadius * cos (fAngle) + 0.5),
				(int) (-fRadius * sin (fAngle) + 0.5)) ;
		}
		EndPaint (hwnd, &ps) ;
		return 0 ;

	case WM_DESTROY:
		DeleteObject (hRgnClip) ;
		PostQuitMessage (0) ;
		return 0 ;
	}
	return DefWindowProc (hwnd, iMsg, wParam, lParam) ;
}
